Before a short description of the present invention is given the definitions of the terminology used in the application is presented.
If nothing else is stated “media signals” and “source material” are defined as representation of the broadcasted signals, on analog or digital form, but the expressions could also defined as any representation at all that make a comparison process possible.
“Search key” is defined as a section of the above given representation, a section that could be very short, of the order of magnitude fractions of seconds, or very long. The actual application of the system and the method determine the length of the search key. In the case the user intends to record music from a radio broadcast the search key could for example be as long as a few music tracks to thereby reproduce a song that does not contain commercials and other unwanted material in the music. The search key can be obtained by manual activation of a key choosing process. In the example relating to radio broadcasted music, a user could for example, activate this process if he or she hears a song on the radio and wants to record it. The user himself will then manually activate the search key process by, for example, pressing a button, and the system will react and pick out a segment of the signal representation as a key and use this segment as a search key in a later comparison process. The key setting process could also be activated automatically, an alternative that will be described in more detail below.
The term “search key” could also be intended as a representation of the above given representation, e.g., a small part that is saved with low band width and than saved, for example, according to a sound compression method.
In the remaining parts of this description the term “search key” will be used interchangeably with the term “search key representation”. The difference between these terms should be clear, since it only relates to what type of representation is given to the original search key.
“An iterative process” is intended as an algorithm that compares segments of signal representations, signal representations that contains an essentially common search key, to obtain longer and longer common segments by using this algorithm. This process can proceed until the system, according to some predetermined growth conditions, terminates the process, for example when the iterations do not give an increased time length for the common signal sequences. If an exact match is obtained between different segments, it is very likely that the representation is a version that does not contain any unwanted signals.
In this application “search track” is defined as the material that is saved and used in the comparison process that saves or deletes the final version of the signal representation, or that logs where this is located in the memory domain.
With this comparison process the search track can be shortened/reduced dramatically by, for example, letting the system remove representations of the source material and only perform searches in the sections of the search track that are relevant for finding new source material.
The search track could, for example, be saved in the frequency domain, as a whole or as a much more compressed search track in order to reduce the required amount of memory or the required amount of processing power.
Other terms used in this application will be defined as it is introduced.
One problem with the procedure according to steps i)-vi) given above is the necessity to save large amounts of source material. The present invention relates to methods for improving this aspect of the system and method according to PCT/US02/05537. Further improvements relate to certain choices of the search key and to the activation of the process/method in the system, and also to different approaches for processing the search track, i.e., the section of the saved signal representation that is searched in order to find essentially identical key representations and which is also used as material for the comparison process in the application PCT/US02/05537. Improvements over the above given system and method are briefly summarised below. They will be described in more detail in a later part of this application.
It is very advantegous if the search tracks, i.e., the materal that is searched and exposed to the comparison process, is normalized when the signals are received. Normalization means that the signal representations are given a common amplitude/sound level the moment they are received. In this manner the number of required computations in a comparison process will be vastly reduced. The reduction of the number of computations follows from the fact that it will not be necessary to normalize the search track for every comparison process.
It is possible to remove masking effects that have been added to the signals. It is thereby possible to save only those parts of the signal representations that can be perceived by the user. This procedure makes it easier for the system to find representations of the search key and makes it possible to reduce the size of the search track.
It is possible to make the the search track and the search key smaller by compressing all signal representations, either by a destructive compression or a non-destructive compression.
Saving compressed representations requires less memory capacity.
A high pass filter could be used to remove DC-currents from the signal representation. This filter could be used for both the search track and the search key. By using a high-pass filter it is possible to give all signal amplitudes a common zero point in the used representation.
It is also very advantegous to give the search track a smaller band width. If the search track/signal representation is saved with smaller band-width the demands on the system's memory capacity can be reduced and the method becomes faster.
The search track, i.e., the source material that contains the signal representations, is preferably processed in such a way as to make it smaller by removing all known unwanted signals. Various methods that make this possible will be described in a later part of this application.
It is very advantegous if only certain selected parts of the representation are saved. In this way the required processing power, the required memory and the number of computations that the system needs to perform are reduced. If the search track is saved for every N:th sample (where N is larger than 1) the memory demands on the system is vastly reduced. This search track can then be compared to a search key that is saved in another format, for example with another value of N. This adds up to a drastically reduced memory demand and/or a faster method, something that in the end makes it possible to produce the product at a lower cost for the customer.
A method according to the present invention aimed to make use of only certain sections of a signal representation yields a more capacity saving system than the system that is used in the comparison process defined above. It is for example possible to use, In case the signal representation is taken from av television broadcast, it is for example possible to use only sound, percentages of pixels of a certain colour, etc.
It should be noted that a system that is constructed to run the method, for example for recording music from a radio broadcast, can reduce the memory capacity and the required processing power by deleting music from the search track (or log where the found music is located). If, by using the method given above, the system already have identified essentially identical search track segments the latter found segments, which were found in the search track by the present method, can be deleted. It is also possible to delete the segments that lie between these segments, if that is desired. The opposite applies to movies, where the interest lies in removing the commercial while leaving the movie unaltered.
Media signals can be saved or deleted during the actual recording procedure, but it is possible to perform this step when the media signals are moved to other memory domains or at the actual display of the signals, the system for example displays a movie without commercials, the commercial is actually there but it will not be broadcasted during the movie broadcast.
Further improvements over the system disclosed in PCT/US02/05537 relate to preloaded lists and afterloaded lists. These will be defined and described in more details below.